Philosophy Of Perception Categories Of Perception

A major issue in the philosophy of perception is the possibility of discrepancies between the external world and the perceiver's impressions, which are sometimes referred to as qualia. While René Descartes concluded that the question "Do I exist?" can only be answered in the affirmative ( cogito ergo sum), Freudian psychology suggests that self-perception is an illusion of the ego, and cannot be trusted to decide what is in fact real. Such questions are continuously reanimated, as each generationGenerations redirects here. For the soap opera, please see Generations (TV series Generation is the act of producing offspring, or procreation. It is also the act of bringing something into being (such as electrical generation and cryptographic code gener grapples with the nature of existence from within the human conditionThe human condition is a term used in literature to describe the joys and terrors of being human, and generally refers to biologically determined events which are common to most human lives. These include: birth childhood adolescence love sex reproduction. The questions remain: Do our perceptions allow us to experience the world as it "really is?" Can we ever know another point of view in the way we know our own?

1 Categories of perception

The philosophy of perception is mainly concerned with exteroception. When philosophers use the word perception they usually mean exteroception, and the word is used in that sense everywhere below.

2 The Scientific Account of Perception

The science of perception is concerned with how events are observed and interpreted. An event may be the occurrence of an object at some distance from an observer. According to the scientific account this object will reflect light from the sun in all directions. Some of this reflected light from a particular, unique point on the object will fall all over the corneas of the eyesThis article refers to the sight organ. See Eye (disambiguation) for other usages. human eye. Note that not all eyes have the same anatomy as a human eye. An eye is an organ that detects light. Different kinds of light-sensitive organ are found in a varie and the combined corneaThe cornea is the curved, transparent layer that covers the front part of the eye and protects its lower structures. Together with the lens, the cornea refracts light and consequently helps the eye to focus. The cornea gives a larger contribution to the t/lens system of the eyes will divert the light to two points, one on each retinaeye cross-sectional view. Courtesy NIH National Eye Institute. Many animals have eyes different from the human eye. The retina is a thin layer of cells at the back of the eyeball of vertebrates and some cephalopods; it is the part of the eye which transdu. The pattern of points of light on each retina forms an image. This process also occurs in the case of silouettes where the pattern of absence of points of light forms an image. The overall effect is to encode position data on a stream of photons and to transfer this encoding onto a pattern on the retinas. The patterns on the retinas are the only optical images found in perception, prior to the retinas light is arranged as a fog of photons going in all directions.

The images on the two retinas are slightly different and the disparity between the electrical outputs from these is resolved either at the level of the lateral geniculate nucleus or in a part of the visual cortex called 'V1'. The resulting single image that forms experience is called a 'percept'.

Recent fMRI studies show that dreams, imaginings and perceptions of similar things such as faces are accompanied by activity in many of the same areas of brain.

If an object is also a source of sound this is transmitted as pressure waves that are sensed by the cochlear in the ear. If the observer is blindfolded it is difficult to locate the exact source of sound waves, if the blindfold is removed the sound can usually be located at the source. The data from the eyes and the ears is combined to form a 'bound' percept. The exact location in the brain of this bound percept is the subject of considerable study.

It should be noted that the scientific account of perception is representationalist because the images on the retinas are 'views' of the physical world. These views are projections of position data from an object onto a 2D plane.

3 Philosophical ideas about perception

The most common theory of perception is naive realism in which people believe that what they perceive is things in themselves. Children develop this theory as a working hypothesis of how to deal with the world. Many people who have not studied biology carry this theory into adult life and regard their perception to be the world itself rather than a pattern that overlays the form of the world. Thomas Reid took this theory a step further, he realised that sensation was composed of a set of data transfers but declared that these were in some way transparent so that there is a direct connection between perception and the world. This idea is called Direct Realism. Direct Realism has become popular in recent years with the rise of postmodernism and Behaviourism. Direct Realism does not clearly specify the nature of the bit of the world that is an object in perception, especially in cases where the object is something like a silhouette.

The succession of data transfers that are involved in perception suggests that the substrate of the percept is actually some form of brain activity and that somehow the brain can perceive itself. This concept is known as indirect realism. In Indirect Realism it is held that we can only be aware of external objects by being aware of representations of objects. This idea was held by John Locke and Immanuel Kant. The common argument against indirect realism, used by Gilbert Ryle amongst others, is that it implies a homunculus or Ryle's regress where it appears as if the mind is seeing the mind in an endless loop. This argument assumes that perception is entirely due to data transfer and classical information processing. This assumption is highly contentious (see strong AI) and the argument can be avoided by proposing that the percept is a phenomenon that does not depend wholly upon the transfer and rearrangement of data.

Direct realism and indirect realism are known as 'realist' theories of perception because they hold that there is a world external to the mind. Direct realism holds that the representation of an object is located next to, or is even part of, the actual physical object whereas indirect realism holds that the representation of an object is brain activity. Direct realism proposes some as yet unknown direct connection between external representations and the mind whilst indirect realism requires some feature of modern physics to create a phenomenon that avoids infinite regress. Indirect realism is consistent with experiences such as:

binding, dreams, imaginings, hallucinations, illusions, the resolution of binocular rivalry, the resolution of pattern rivalry, the modelling of motion that allows us to watch TV, the sensations that result from direct brain stimulation, the update of the mental image by saccades of the eyes and the referral of events backwards in time

whereas direct realism argues either that these experiences do not occur or avoids the problem by defining perception as only those experiences that are consistent with direct realism.

Apart from the realist theories of perception there are also anti-realist theories. There are two varieties of anti-realism: Idealism and Skepticism. Idealism holds that we can only be aware of mental things whereas skepticism holds that because we never perceive external objects directly we can never know for certain whether they exist. One of the most influential proponents of idealism was George Berkeley who maintained that everything was mind or dependent upon mind. Berkeley's idealism has two main strands, phenomenalism in which physical events are viewed as a special kind of mental event and subjective idealism. David Hume is probably the most influential proponent of skepticism.

4 Cognitive Processing and Epiphenomenalism

Perception is sometimes referred to as a cognitive process in which information processing is used to transfer information from the world into the brain and mind where it is further processed and related to other information. Some philosophers and psychologists propose that this processing gives rise to particular mental states ( cognitivism) whilst others envisage a direct path back into the external world in the form of action (radical behaviourism).

Many eminent behaviourists such as John B. Watson and B.F. Skinner have proposed that perception acts largely as a process between a stimulus and a response but despite this have noted that Ryle's "ghost in the machine" of the brain still seems to exist. As Skinner wrote:

"The objection to inner states is not that they do not exist, but that they are not relevant in a functional analysis" Skinner 1953.

This view, in which experience is thought to be an incidental by-product of information processing, is known as epiphenomenalism.

5 Perceptual Space

Another aspect of perception that is common to both realists and anti-realists is the idea of mental or perceptual space. David Hume considers this at some length and concludes that things appear extended because they have the attributes of colour and solidity. A popular modern philosophical view is that the brain cannot contain images so our sense of space must be due to the actual space occupied by physical things. However, as Rene Descartes noticed, perceptual space has a projective geometry, things within it appear as if they are viewed from a point and are not simply objects arranged in 3D. Mathematicians now know of many types of projective geometry such as complex Minkowski space that might describe the layout of things in perception. It is also known that many parts of the brain contain patterns of electrical activity that correspond closely to the layout of the retinal image (this is known as retinotopy ). There are indeed images in the brain.

6 See also

A cognitive process is a mental route of absorbing knowledge and subsequent recollection.

Two cognitive processes are organization and integration of thought. Organization of thought sorts and makes comprehensible. Integration of thought builds to application or purpose.

Philosophy of mind Epistemology Perception

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